In a multi-cylinder internal combustion engine (hereinafter simply referred to as an engine) for a vehicle, for example, an air intake control valve is known to be provided at an air intake system including a port and a surge tank. Such air intake control valve includes a body extending so as to divide an inner portion of the surge tank into two portions, a valve element operated to rotate so as to open and close a fluid passage formed at the body, and a seal member sealing between an inner surface of the surge tank and an outer periphery of the body. The air intake control valve is mounted so as to close a connection bore formed at a partition wall separating the inner portion of the surge tank into the two portions, i.e., two chambers. The valve element of the air intake control valve is appropriately driven to rotate by an actuator so as to obtain a connected state where the two chambers are connected to each other and a disconnected state where the two chambers are disconnected from each other. As a result, a resonance frequency of the air intake system is changed to thereby obtain a supercharging effect over a wide range of an engine operation. In a case where an air leakage increases between the two chambers (upper and lower chambers), an expected resonance frequency may not be obtained in the air intake system of the engine, which leads to a deterioration of the supercharging effect.
JP2004-116357A (hereinafter referred to as Reference 1) discloses such air intake control valve as illustrated in FIGS. 9A and 9B in which a gasket (seal member) 67 formed into a string shape and made of an elastic material is attached to an outer periphery of a frame (body) 62 holding a valve element. In a case where the body 62 is attached to a sealed surface 66f of a partition wall formed at a surge tank, a gap between the sealed surface 66f and the body 62 is sealed by the seal member 67 that is pressed against the sealed surface 66f of the partition wall. As a result, an air leakage between two chambers (upper and lower chambers) is restrained.
As illustrated in FIG. 9A, according to the air intake control valve disclosed in Reference 1, the seal member 67 includes a fitting portion 68 fitted to a seal groove 62D that is formed at the outer periphery of the body 62. The fitting portion 68 substantially includes a rectangular cross section. The seal member 67 also includes an end seal portion 69 vertically extending from the fitting portion 68 towards the sealed surface 66f. The end seal portion 69 substantially includes a semicircular cross section symmetric to a divided surface constituted by the body 62 so as to divide an inner portion of the surge tank into two portions. In a case where the body 62 is attached to the sealed surface 66f, the end seal portion 69 is squashed towards the fitting portion 68 by the sealed surface 66f while the symmetric shape of the end seal portion 69 relative to the divided surface is maintained as illustrated in FIG. 9B. According to the aforementioned structure, in order to restrain the air leakage because of the deformation of the end seal portion 69 in an oblique or lateral direction that is caused by a high air pressure from either of the upper and lower chambers, a rigidity to some extents may be required to the end seal portion 69. Therefore, an apex angle of a triangular-shaped cross section constituting the end seal portion 69 may be inhibited from having too acute angle and additionally the end seal portion 69 may be made of a material having relatively high rigidity.
As a result, in a case where the body 62 is attached to the sealed surface 66f, a large load is necessary for bringing the end seal portion 69 having the semicircular cross section to be deformed so as to be compressed against the fitting portion 68. A contact area between the sealed surface 66f and the end seal portion 69 also increases, which may lead to an increase of a contact pressure or a frictional resistance, for example, acting between the sealed surface 66f and the end seal portion 69. Consequently, the attachment of the body 62 relative to the sealed surface 66f may be difficult.
In addition, in a case where the body 62 is attached to the sealed surface 66f, the fitting portion 68 of the seal member 67 is likely to disengage from the seal groove 62D formed at the outer periphery of the body 62 or to be partially pulled out in a direction where the body 62 is attached because of the high contact pressure, the frictional resistance, and the like acting between the sealed surface 66f and the end seal portion 69. Thus, the sealing ability of the end seal portion 69 may be deteriorated. Further, the body 62 may be deformed by a reaction force that is generated at the body 62 by means of the end seal portion 69, which may lead to the air leakage between the body 62 and the fitting portion 68 of the seal member 67.
In Reference 1, the seal member 67 may have an arched shape in a cross section by including a groove portion 70 having a tunnel shape at a lower end of the fitting portion 68 to thereby reduce the reaction force generated at the fitting portion 68 of the seal member 67. However, because of the high rigidity of the material constituting the seal member 67, an easy deformation is insufficient for the entire seal member 67. As a result, a large compression by a low load may be impossible and therefore an issue of an excessive load when the body 62 is inserted into the sealed surface 66f may not be effectively dissolved.
JP63-156422U discloses an air intake control valve including two projections that serve as the end seal portion so as to extend in parallel to a divided surface constituted by a body. However, in the same way as Reference 1, each of the projections vertically projects towards a sealed surface, which may also raise issues such as a difficulty in attaching the body to the sealed surface, the deterioration of the sealing ability because of the disengagement or the pull-out of a fitting portion of a seal member, an air leakage caused by the deformation of the body, or the like.
A need thus exists for an air intake control valve which is not susceptible to the drawback mentioned above.